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The Standard Model

This diagram shows the particles that make up the Standard Model of particle physics, including the recently discovered Higgs boson. The particles of matter, on the left, are divided into two groups. The particles in one group stick together to make bigger particles, like the protons and neutrons in the nucleus of an atom. Particles in the other group exist on their own, such as the electrons outside an atom’s nucleus, and neutrinos, which are created by the nuclear reactions inside stars. The matter particles interact by exchanging other types of particles, known as force carriers, which act as the glue that holds atoms together and the messengers that travel through the universe as light. The Higgs gives mass to all the particles of matter. [Fermilab]

Particle physicists recently added the last piece to a model of the universe. The model is built of bits of matter and bits that allow matter to interact. It’s been poked and jiggled by every test that scientists can think of, yet it still stands.

It’s called the Standard Model, and it’s been developed over the last few decades. It splits the universe into two kinds of particles.

First are the particles of matter, which are divided into two groups. The particles in one group stick together to make bigger particles, like the protons and neutrons in the nucleus of an atom. Particles in the other group exist on their own, such as the electrons outside an atom’s nucleus, and neutrinos, which are created by the nuclear reactions inside stars.

These particles interact by exchanging other types of particles, known as force carriers. They act as the glue that holds atoms together and the messengers that travel through the universe as light.

The final piece of the Standard Model is the recently discovered Higgs boson. It gives mass to all the particles of matter. Without the Higgs, those particles couldn’t join together to form stars, planets — and people.

Yet the Standard Model has some gaps. It doesn’t incorporate gravity, for example. It can’t explain why there’s more matter in the universe than antimatter. And it can’t explain mysterious dark matter. But scientists are working on extending the model — and we’ll talk about that tomorrow.

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